1. Field of the Invention
The present invention relates to a semiconductor light emitting device, and more particularly, to a non-polar nitride-based light emitting device and a method for fabricating the same.
2. Discussion of the Related Art
Gallium nitride (GaN) used as a material of a semiconductor device, such as a blue light emitting diode, has a Wurzite crystal structure, and is grown as a thin film mainly in a c-plane crystal direction. The reason for this is that growth of GaN in the c-plane crystal direction facilitates horizontal growth and thus forms a high-quality thin film having minimum defects, such as dislocation.
Here, GaN has a crystal structure in which a nitrogen layer and a gallium layer are alternately repeated in the growth direction. Therefore, a strong internal field is present between nitrogen and gallium and thus polarization occurs.
The internal field is divided into two components, such as spontaneous polarization and piezo-electric polarization, and if a layer having a different lattice constant, such as an InAlGaN layer, is inserted, polarization increases and thus quantum confined stark effects may occur.
For example, in a structure in which an InAlGaN active layer is inserted between p-type and n-type GaN layers, as in a blue light emitting diode, deformation occurs between the layers due to a lattice constant difference, and such deformation may generate an internal field and cause warpage of an energy band structure of the active layer.
Consequently, wave functions of electrons and holes within the active layer are spatially separated and the size of an energy gap is greatly reduced, and this may cause lowering of recombination efficiency.